Calcutta, May 4: A gang of four walked into a cellphone shop off a busy road in south Calcutta this afternoon and shot dead the woman at the counter, in what police think is an extortion killing.

Reshmi Mahnot, 30, whose husband owns the Nokia outlet Elekrocrafts on Lake Terrace, off Lansdowne Road, was in the shop as usual with her father-in-law Dalpat Mahnot.

A cellphone demonstrator, a Nokia serviceman and a bag supplier were also present when the four arrived at 2.15 pm, pretending to be customers, deputy commissioner of police (south) Anuj Sharma said.

'After asking Reshmi to show a cellphone, one of them brandished a revolver and opened fire. As (Dalpat) Mahnot tried to push away the revolver, another youth hit his hands with a bhojali,' said Salma Khatun, the cellphone demonstrator.

'One of the men who stood guard in front of the shop downed its shutter seconds before his associate pulled the trigger,' she added.

The gang then stepped out of the shop, located near National High School for Girls, and got away in a taxi.

Reshmi, who has a five-year-old son, and 62-year-old Dalpat were taken to the nearby Ramkrishna Mission Seva Pratisthan, where she battled for life for two hours. But the bullet had pierced her liver. She died at 4.30 pm.

'On hearing a hue and cry, I rushed only to see the woman lying on the floor. Blood was oozing out from the wound on her abdomen. We immediately rushed her and Mahnot to the Ramkrishna Mission Seva Pratisthan,' said Bapi Bhaduri, a neighbour.

Reshmi's husband Vishal was informed and he arrived at the hospital soon after. After she died, he went home to his son Yash. The family lives at Lake Gardens. When contacted, he said: 'I have no idea why it happened and who the attackers were.'

But during the investigation, police found that the Mahnots had received extortion calls. 'The Mahnot family had got possession of another shop on Lansdowne Road in March. They were supposed to open another cellphone outlet in August,' said an officer of the detective department's homicide wing.

The first extortion call had come a few days ago, police said. 'The extortionists were asking for Rs 5 lakh from Vishal. But he refused,' said the officer.

The police believe the extortionists were behind the murder. 'Those who witnessed the incident confirmed that the miscreants did not ask for money. And before fleeing, they showed no interest in cash and the cellphones kept in the showcase,' said another officer of the detective department, arguing that robbery could not be the motive.

The police are looking for a criminal, identified as Amit, and have detained four persons for questioning.